Dimensional image display devices are used to create visual effects such as, for example, 3D effects, animation, depth, and other such types of graphics. The dimensional image display devices can be applied to various articles as eye-catching promotional tools, advertising, branding, games, and the like because the dimensional images offer eye-catching images by providing multiple images and/or animation. Examples of articles can include, for example, containers, cups, packaging, wrappers, tubes, envelopes, greeting cards, invitations, napkins, posters, business cards, fabrics and clothing, billboards, stickers, labels, badges, pens, magnets, postcards, identification or gift cards, and any of a variety of articles.
Dimensional image display devices typically incorporate a printed image proximate a lens array. The printed image can be either directly bonded or printed to the lens array, or printed on a separate substrate and laminated to the lens array. Image segments or elements are printed using high resolution, and precise registration techniques to form the overall image. One such printing technique includes interlacing images, in which a composite of two or more images are interlaced with each other in individual slices or segments to form the overall image that will be viewed through a lens array. The interlaced image is then configured or mapped so that each lens of the array focuses on at least a portion of the interlaced image. The interlaced image is configured to accommodate both viewing distance and curvature through the lens.
Ink-to-ink registration is a term of art that describes the placement accuracy of different, or overlapping colors in relation to one another on an image, such as an interlaced image, from a four color process (4-CP) separation or other printing technique. When printing an image that has more than one color, depending on the method of printing, it is necessary to print the image or image element a separate time, and/or on multiple units, for each separate color. So that the final image is consistent, and so each of the colors lines up correctly, a system of registration is necessary. Ink-to-ink registration accuracy is particularly important in printing of interlaced images, as poor registration accuracy can result in a low quality dimensional image, such as image ghosting or color shift, loss of distinct motion, and the like, therefore creating excess waste and expense.
Lens-to-ink registration can be defined as the registration accuracy of the image or image elements to the lenses of the lens array. Lens-to-ink registration accuracy is critical in dimensional image display devices as poor lens-to-ink registration accuracy can also result in loss of distinct motion, unfocused or unrecognizable images, flipped or otherwise skewed images, and the like, again creating excess waste and expense.
One type of dimensional imaging technology well-known in the art includes lenticular image technology. Lenticular image technology includes a lenticular image, such as an interlaced image, in combination with a lenticular lens array. The lenticular lens array is formed from a web or sheet including a plurality of substantially parallel elongated cylindrical lenticules or lenses on one surface. The second surface is planar. Typically, the lenticular lens array is formed from a plastic material and can be formed from any of a variety of techniques including casting, coating, embossing, extruding, and the like. The interlaced image can be printed directly on the planar second surface, or can be printed on a separate substrate and subsequently laminated to the lenticular lens array by a clear adhesive, fusing, or other similar techniques. Examples of lenticular image technology can be found in U.S. Pat. Nos. 6,900,944 to Tomczyk; 6,424,467 to Goggins; and 7,359,120 to Raymond et al., the disclosures of which are incorporated herein by reference.
Currently available methods can provide a lens sheet or lenticulated sheet array, which can vary in thickness or caliper, for example, from about 10 mils to about 40 mils. The thickness of the extruded lenticular lens layer is suggested by the formula: r=C×f or r=[(n′−n)/n′]×f where r is the radius of curvature of a lenticular lens, C is a constant, f is the focal length of optimal focus thickness for the plastic, n′ is the index of refraction of the lens construction material, such as an extruded plastic, and n is index of refraction of air. From the formula it is evident that the thicker the plastic the lower the pitch or lenticules per inch (LPI) and the lower the pitch, the coarser the lens. A coarse lens can give undesirable lens effects, for example, distortion of an underlying image. A coarser lens requires image graphics and text to be significantly large to avoid lens undesirable lens effects. When printing a lenticular image on a lenticular lens, the lens needs to be parallel to the interlace image, such as, for example within +/−½ lenticule per ten inches. If this is not maintained, the image does not have an acceptable vertical flip, but rather a skewed flip. Skew can be defined as unacceptable ink-to-lens registration accuracy of the vertical lenticular image elements to the vertical lenticular lenses.
Another type of dimensional imaging technology includes fly's eye or bug's eye image technology. Fly's eye or “integral” lens arrays are formed from a web or sheet including a plurality of domes or semi-circular structures, rather than the elongated lenses of lenticular technology. Similar to lenticular, an image, such as an interlaced image, can be printed on the planar side of the lens sheet or web, or printed on a separate substrate and laminated thereto. There are a number of benefits to using a fly's eye lens as opposed to a lenticular lens. The fly's eye lens is essentially a lenticular lens in multiple directions tangentially around the lens. This essentially allows one not only to interlace an image from left to right (horizontal direction), but also up and down (vertical direction), diagonally, or any combination thereof to give additional animated effects.
Current methods of producing dimensional images, such as lenticular images, include printing of lenticular sheets through a sheet fed press where, as discussed above, the caliper ranges from about 10 mils to about 40 mils. These sheets then go through additional offline processing steps. The result is an expensive lenticular display device with a limited number of applications because of its rigidity due to its overall thickness. At least two factors drive the cost of the lenticular display device: the amount of plastic used in creating the lens, and the number of process steps that are needed to print and convert a lenticular product.
To reduce the cost of manufacture by reducing the amount of plastic used, a lens sheet having a thinner caliper or gauge thickness is used, such as, for example, a lens sheet of about ten mils or less. When using a thinner lens, the pitch, or number of lenses per inch, is higher based on the formula described above. As the pitch increases, a width of each image element or slice of the interlaced image becomes thinner, which in turn makes ink-to-ink registration accuracy and resolution more critical. It has been found that ink-to-ink registration accuracy on a thinner caliper lens plastic sheet on a sheet fed press is extremely difficult, resulting in poor quality images.
Secondly, by switching the current sheet-fed process to a web press with inline laminating and finishing capabilities, it is possible to significantly reduce cost due to fewer process steps. Web presses are suited for running and printing thinner substrates and can have optional inline finishing capabilities, such as lamination and converting. However, web presses tend to have less ink-to-ink registration accuracy from color to color than sheet fed presses because the web tends to wander or “walk” from side to side through the press ink units if not tightly controlled. In particular, there tends to be more movement of the web as the caliper is decreased, especially if there is significant gauge thickness variation. Further, such problems can be exacerbated with thin films and substrates as a result of baggy edges of the web in the positions where web guidance devices read guidance information, thereby misguiding the web. Such devices are often expensive and temperamental or difficult to control within the tolerances needed for dimensional image display devices.
Attempts have been made to produce a high definition thin lenticular lens for viewing interlaced images. U.S. Pat. No. 6,424,467 to Goggins describes a high definition lenticular lens having an arc angle greater than about 90 degrees and a width of less than about 0.0067 inches (6.7 mils). The lens has a gauge thickness that is equal to or substantially equal to the focal length. However, the Goggins disclosure is limited to the lens array material, and does not address the printing or printing registration issues discussed supra. U.S. Pat. No. 7,359,120 to Raymond et al. discloses a method of manufacturing a device for displaying an interlaced image including creating an “ultrathin” lens array in the film by forming lens sets, and bonding an interlaced image including sets of elongate image elements to a second side of the film. Each of the lens sets is configured with lenses for focusing light from one of the image elements in a particular paired set of image elements by creating a unique configuration or cross-sectional shape for each lens of the lens set. The fabrication of the device can be done using a web process. The Raymond et al. disclosure, however, does not discuss the ink-to-ink registration issues, and rather focuses on eliminating the critical thin resolution of particular image elements that would otherwise be needed in traditional lenticular image technology.
Therefore, there remains a need for a dimensional image display and method of making such that would eliminate the need for critical ink-to-ink registration accuracy such that the finished piece or article would virtually always give a dimensional or motion effect when printed using a web press at any lens gauge thickness and pitch.